The underlying basis of liver disease is the hepatic failure that results from hepatocyte injury and subsequent cell death. To be able to prevent this hepatic damage, it is necessary to better understand the mechanisms of hepatocyte injury. While the mechanisms of damage for specific hepatotoxins have been well studied, the modulation of this injury by external factors and cytoprotective proteins, has not been well investigated. External factors involved in the process of acute liver injury, such as the cytokines, tumor necrosis factor-alpha (TNF- alpha) and interleukin-1 (IL-1), have begun to be identified. Our long- term goal is to determine the roles of these modulators of acute liver damage through the study of cell culture models and further in vivo investigations, in order to understand the mechanisms of hepatic injury. The specific aims of this proposal are: (1) To examine the role of TNF- alpha, IL-1 and lipopolysaccharide (LPS) in acute liver damage. This work will involve the use of an in vitro model of galactosamine (GalN) liver injury using cultures of the hepatoma cell line HUH-7 alone, or in coculture with the macrophage line U-937. This model will be used to study the effects of TNF-alpha, IL-1, and LPS during toxic injury. Additional investigations will examine the influences of macrophages on these effects, as well as the mechanisms of cytokine toxicity. In vivo studies will also further define the roles of LPS, TNF-alpha and IL-1. (2) To investigate the function of anti-oxidant enzymes and metallothionein (MT) in the protection against TNF-alpha IL-1 mediated hepatocellular injury. These studies will also include an examination of the in vivo models of CCl4 and GalN injury for changes in gene expression and protein synthesis of potentially cytoprotective proteins. (3) To determine additional cellular factors responsible for hepatocyte resistance to oxidative injury. HUH-7 cells resistant to H2O2 will be selected for the purpose of determining which genes are overexpressed in these cells, and whether they mediate resistance to H2O2 and other forms of oxidative stress.